City	Sow outdoors	Last frost
Philadelphia	Apr 13 to Apr 27	Mar 30
Pittsburgh	May 2 to May 16	Apr 18
Allentown	May 4 to May 18	Apr 20
Reading	Apr 28 to May 12	Apr 14
Erie	May 10 to May 24	Apr 26
Bethlehem	May 4 to May 18	Apr 20
Scranton	May 7 to May 21	Apr 23
Lancaster	May 3 to May 17	Apr 19
Levittown	May 5 to May 19	Apr 21
Harrisburg	Apr 29 to May 13	Apr 15
York	May 10 to May 24	Apr 26
Wilkes-Barre	May 7 to May 21	Apr 23
Altoona	May 9 to May 23	Apr 25
State College	May 4 to May 18	Apr 20
Penn Hills	Apr 30 to May 14	Apr 16
Norristown	Apr 22 to May 6	Apr 8
Chester	Apr 13 to Apr 27	Mar 30
Mount Lebanon	May 2 to May 16	Apr 18
Bethel Park	May 2 to May 16	Apr 18
Easton	May 2 to May 16	Apr 18
Hazleton	May 14 to May 28	Apr 30
Drexel Hill	Apr 16 to Apr 30	Apr 2
Monroeville	May 6 to May 20	Apr 22
Williamsport	May 9 to May 23	Apr 25
Lebanon	May 4 to May 18	Apr 20
Plum	Apr 30 to May 14	Apr 16
King of Prussia	Apr 22 to May 6	Apr 8
Chambersburg	May 2 to May 16	Apr 18
Pottstown	May 4 to May 18	Apr 20
Carlisle	May 7 to May 21	Apr 23
Allison Park	Apr 30 to May 14	Apr 16
New Castle	May 14 to May 28	Apr 30
Murrysville	May 6 to May 20	Apr 22
Baldwin	May 2 to May 16	Apr 18
Phoenixville	May 2 to May 16	Apr 18

Questions

When should I plant pumpkins in Pennsylvania?

In Philadelphia, sow outdoors from April 13 to April 27. Across Pennsylvania the window opens between April 13 and May 14, depending on the local last frost.

How is this date worked out?

Sow outdoors 2–4 weeks after the last frost. Frost dates are NOAA 1991–2020 averages for the weather station nearest each city.